Method of fermenting solutions and producing yeast



June 8, 1937. HSCHOLLER ET Al. l 2,083,347

METHOD OF FERMENTING SOLUTIONS AND PRODUCING YEAST Filed Septl 24, 19542 Sheets-Sheet 1 June 3, 1937 H. scHoLLl-:R ET Al. 2,083,347

METHOD 0F FERMENTING SOLUTIONS AND PRODUCING YEAIST v Filed Sept.24,-1934 2 Sheets-Sheet 2 Patented June 8, 1937 ME'rnon or FERMENTINGSOLUTIONS AND raonUclNc. YEAs'r Heinrich Scholier, Solln, near Munich,and Rudolf Eickemeyer, Tornesch/Holstein, Germany Application September24, 1934, Serial No. '145,340

In Germany January 10, 1933 14 Claims. (Cl. IBS-94) This inventionrelates to a process for the improved and more particularly acceleratedproduction of yeast and for the fermentation of'solu.- tions. 'Ihemethod permits yeast to be obtained,

and fermentation processes to be carried out, both continuously as wellas intermittently. The method depends upon a combination of static anddynamic conditions, more particularly on the action of streamingconditions on suspensions and the deposition thereof and enables aconsiderable growth in the yeast and the separation of the same from thenutrient liquid to be carried out "in a single operation with thecomplete utilization of all nutrient constituents. The new method isalso applicable when the obtention of yeast in substance ldoes not comeinto question but only its use for' biologically acting on the liquid,i. e., 1fokr carrying out fermentationprocesses or the In the followingthe expressions: fermentation, fermentation apparatus, fermentationliquid, fermented liquid and the like, are employed in theY widest senseof the words, and therefore, even when it is in essential a matter ofproducing the yeast and not a matter of fermentation in the narrowersense of the words.

It is to be distinctly understood that' the term yeast is usedthroughout this specification and the claims appended thereto in thewidest sense 30 of the word. It includes all varieties of yeast,

amongst which may be mentioned top-fermenting and bottom-fermentingyeast, as well as culture yeast and so-called nature yeast.

Processes are already known for making yeast D with continuous anddiscontinuous supply of the fermentation liquid.

. It has already been proposed continuously to separate the yeast duringthefermentation but the manner of attaining thisend has not yet 40 beenfound.

For the purposes ofthe fundamental explanation of the essential idea ofthe present invention the followingis premised:

According to the invention fermentation liqholds the yeast cells presentpartly in suspension,

whilst another part of the yeast present gradu.

ally settles on steep .inclined surfaces disposed in the fermentationchamber and slides to the reached a certain layer thickness. In order tocarry this lprinciple into effect operations are4 55 Whereas in theusual processes the quantity of uid flows through the fermentationchamber and bottom as soon as the deposited yeast mud has yeast presentamounts to onlya few percent of the total nutrient substances andfermentation products present, the present method is advantageouslycarried out with quantities of yeast which are greater than thequantities of nutrient substances or fermentation productsV present.

The yeast masses which deposit copiously on the inclined surfacesparticularly when using high yeast concentrations and which fall down tothe bottom can be resuspended in the lower part of the fermentationchamber, for example by means of suitable mechanical stirring devices orelse by I stirring with air or other gases. A part of the eitherintermittentlyor continuously, by letting olf through a sluicearrangement, and if necessary thoroughly washed in the known manner, andmay be worked up to a dry product.

If the withdrawal of the yeast is effected corresponding to the yeastgrowth then the yeast concentration in the fermentation chamber can bekept constant in this way. The fermentation liquid flowing through thefermentation chamber leaves the top of the vessel afterv the nutrientsubstances contained in it are more or less consumed by the yeast andthe yeast suspended in it is wholly or for the mostpart deposited.

.In order to secure a. better effect vertical guid# ing surfaces arepreferably disposed in the middle of the fermentation apparatus, saidsurfaces being tubularly or prismatically arranged. For the purposes ofbetter explanation in the following three zones are distinguished withinthe fermentation vessel (cf. Figure 4):

1. The suspension zone 50, which is surrounded by the vertical guidingsurfaces and in which the yeast is kept ln suspension in a highconcentration by the upwardly flowing liquid;

2. The settling zone 52 which is disposed outside the suspension zoneand in which the velocity of now is retarded and the direction of flowmay even be reversed, so that the yeast has an op. portunity to 'settleon the inclined surfaces and to slide down;

3'. In between the suspension zone and the settling zone there may alsob e the circulation zone 5I in which the fermentation liquid left movesfrom the top to the bottom and again enters the suspension zone.

The cross section of the suspension zone is preferably dimensionedsothat the velocity of ow in that zone is automatically It has now beenfound to be advisable to supply a part of the yeast leavingthesuspenslon zone, and may be also a part of the yeast slidingdownwardly on the inclined surfaces, back into the suspension zone againin order to be able to maintain the desiredhigh yeast concentration.This is effected by bringing about additional upward motion of theliquid in the suspension zone by suitable means. In this way the liquidcoming over the top of the suspension zonesinks downwardly outside thiszone into the so-called circulating zone and through openings providedat the lower end of the suspension zone enters into this latter again,carries along with'it the yeast suspended therein and in certain casesdrags with it an excess of deposited yeast which may be present andresuspends it. `The additional upward motion of the liquid withinthesuspension zone can be effected in various ways, for example by meansof a propeller stirring mechanism which can simultaneously subdivideagain and suspend the excess yeastmud, or with avoidance of mechanicaldevices, by blowing in gases, e. g. air, at the bottom ofthe suspensionzone, in which case the air supplyV preferably has a cross sectionsomewhat smaller than that of the suspension zone so that an injectionaction is produced as a result Vof which'the excess yeast mud can bedrawn up and suspended.

In the sameA way the gas blown in also acts according to the principleof the Mammut pump. It has been found that the desired eifect can be.produced in a particularly efficient manner by fine aeratidn.

, In order to produce better separation of the yeast -it is advantageousto install within 'the settling zone verticalpor approximately verticalsurfaces which again may be arrangedin circular or prismatic fashion andhave the object of compelling the liquid to reverse. These reversalsurfaces are referred to as recoil surfaces.

A special form of the method consists in regulating the velocity of flowthrough the apparain order, for the purpose of effecting-further workingvup or deposition, to be subjected to a single or many times repeatedtreatment in the same or a similar manner. y

Further, operations may also be carried out so that no withdrawal ofyeast takes place within the first4 fermentation apparatus and aquantity of yeast corresponding about to`the growth of the yeastsuspended in the issuing exhausted fermentation liquid leaves theapparatus, then to be separated off in a suitable manner e. 8. by meansof centrifuges.v

This manner of working, which avoids automatic separation of the yeastin the fermentation vessel or at least in the'flrst fermentation vessel,has, as compared with the `usual yeast cultivation process, the furtheradvantage that it operates continuously and moreover occupies onlycomparatively small space. The fermentation apparatus according to thepresent invention may be connected both in series as well as inparallel. The output capacity of the apparatus is, amongst otherthings,l dependent on the size of the inclined surfaces present. It` hastherefor been foundpreferable to arrange several inclined surfaces oneabove the other, the downwardly slidingyeast, without being stirred upor phosphate precipitates.

face is the greater the longer it is. It is preferable, therefore, so toadjust the streaming velocity over the individual inclined 4surfacesthat the time of flow through. just suillces to' give the yeastopportunity to settle, in other words the rate of flow over theindividual inclined surfaces is inversely proportional to the length ofthe inclined surfaces.

It is already known to promote the flocculation of yeast fby addingalkali and by production of It is already known to bring vabout asimilar action by means of flock lactic acid bacteria (referred to inGerman as Flockenmilchsurebakterien"). 'I'hese known expedients can be-used in the present case, the

ncorresponding agents being added either in the settling zone oroperations being carried out right from the start under conditions whichare favourable for flocculating out yeast. Also yeasts which tend toproduce flocculation may be employed in the process right from thecommencement.

The apparatusis `put into operation in the known manner by means ofpitching yeast which is added, preferably in the form of mud,|chiefly inthe suspension space, whilstV the settling and circulation zones` arefilled with water. Tlie addition of fresh seeding material may also beeffected during the continuousvoperation for the purpose of refreshingthe yeast, and takes place preferably within the suspension zone. Ifnecessary, the lead for the fermentation liquid can be used as well forintroducing fresh seeding material if a proper pipe for this purpose,like the lead for the fermentation liquid, is not provided. It is knownto be advantageous in many respects to vsubject the yeast, before it issupplied to its purpose of use, to a ripening process, inasmuch as thetime the yeast remains in the lower part of the settling and circulationzones is insufficient for ripening, the ripening of the withdrawn yeastmay take place in the known manner in a subsequently arranged vessel.Owing to the high yeast'concentration the method is comparativelyresistant to infection. However, owing to its small space .requirementand the continuous manner of working the method may be carried out in Vmentation poisons is reduced or obviated when -the quantity/ofpoison'gaining access to each yeast cell/ is on an average very small.The higher,- therefore, theyeast concentration can be maintained theless harmful do the poisons become. As an example of such a fermentationpoison may be mentioned, for example, aldehydes, which occur more orless regularly in wood sugar liquors. By employing the process accordingto the present invention these substances lose their harmful action sothat it is not necessary to pay particular attention to the presence ofthese substances. Wood sugar liquors,- therefore, can ,be forthwithused-for preparing yeast according :to the present invention, whereas inthe process heretofore employed sulphitehadfto be added in order todeprive the aldehydelofitspoisoning lA .further special advantage isthat the socalled humin substances contained in the wood sugar liquorare prevented from settling since the fermentation liquid (wood sugarliquor with nutrient salts) flows through the apparatus in acomparatively short time according to the present method. In the case ofsmall apparatus.

method of carrying out the process and the ap-.

paratus necessary therefore. In the accompanying drawings:

Fig. 1 is an axial sectional elevation through a fermentation apparatuswith simple treatment device;

Fig. 2 is a detailed representation on a larger scale of the part S ofFig; 1;

Fig. 3 is a sectional elevation through an improved form of fermentationapparatus (yeast production vesse1),such as is particularly suitable forcarrying out the process on a large scale.

Fig. 4 shows the subdivision into zones oi4 the fermentation vesselaccording to Fig. 2.

In Fig. l, I is an inverted conical or pyramidal vessel into which isled in the proximity of the bottom an air or gas supply pipe 2 with aregulating cock 3 and a ne aeration device d, which is provided at thetop with a filter plate 5 or the like. The supply pipe 6 is for thenutrient solution and has the regulatingv valve I and a funnelshapedwidened portion 8 at the' lower end thereof (see also Fig. 2) which isclosed underneath and has eYit orifices at the top. Tubular or pipemembers 9, i0, II, I2, of cylindrical or polygonal cross section, andopen at the bottom and the top, dip into the funnel-shaped vessel I atthe top thereof; the members with even reference numerals projectsomewhat out of the funnel-shaped vessel I, whilst those with oddreference numerals are cut o at about the same level as the upper edgeof the vessel or somewhat below this level.

An overflow channel I3, with one or several outlets Id, is provided.Closable disks, plates or the like, I5, are provided for letting o theyeast mud. Y The' arrows indicate the most important directions of -owof the gases and liquids.

The procedure according to this invention is as follows:

First consider the funnel-shaped vessel I to be full of liquid (nutrientsolution). Fresh nutrient solution is then supplied downwardly throughthe pipe 6 up to the proximity of the filter plate 5 for the air supply.The air streams upwardly in ne small bubbles and, in accordance with theinjector or Mammut principle, causes the liquid with a large part of theyeast suspended'therein to be guided upwardly again within the pipe 9,as a result of which the yeast has opportunity to grow copiously in thefresh nutrient solution. When Athe liquid stream reaches the top of thepipe 9 it tends to spread' radially outwards, but

soon comes up against the projecting end of the pipe I0 and is theredownwardly deflected in the annular space between 9 and I0. The pipe IIIterminates at a distance from the side wall of the funnel-shaped vesselsuch that if necessary a part of the now downwardly moving suspension isled back by the injector action of the aeration device into theascending current within the pipe Sand in this way continuouslycirculates there. Another part of the suspension follows the directionof flow which branches oil at the lower end of the pipe I0 and is againbrought to the top in the annular space between pipe I0 and pipe Il,where it spreads out in a radial direction again over the top end of thepipe Il, is checked again by the pipe I2 as in the case of the pipe Ill,flows down the annular space between pipe I I and pipe l2, divides anewat the bottom of pipe I2, and

At the first branching point of the direction of ow (at Il in Figure 1)there is such a check according to the invention that the specificallyheavier yeast parts, the settling tendency of which. within thepipe 9has been compensated for and overcome by the action of the ascendingsmall bubbles of air, separate to a considerable extent from the owingliquid, corresponding to the gravity, sink down on to the Wall of thefunnel-shaped vessel l and then under the action of gravity fall'intothe lowest part of the vessel, where they either collect around the airsupply pipe and can be drawn on from time to time, or where they canbecontinuously withdrawn by means of suitably opened withdrawal valves orslides.

The circulation flow, which now forces the liquid upwardly again in thespace between pipes I0 and Il, takes a part of the yeast with it againbut in a much smaller quantity than formerly since there is no airstream here, which latter of course has already left the apparatus againat the .top of pipe 9, and since the rate of flow is lower. Theseparation process is repeated at I8 insofar as the suspension stillcontains yeast, and the method may be conducted so that the liquid cannow be led away practically without any loss in yeast. If the necessityshould arise there is noth.

- of repose in such a Way that, bearing'in mind the surrounding liquidmedium, a too thick collection of yeast on the wall of the vessel isavoided.

In order to regulate the flow both as regards i its direction as well asits partial speed rotatable flaps I6 are provided which enable the crosssection of the liquid between the lower end of the pipe in question andthe outer wall of the funnelshaped vessel to be varied at suitableplaces. These flaps serve more particularly to reduce the impact of thelaterally deviated parts of the liquid on the yeast which slides down onthe lateral wall. In this way any upsetting of the process is prevented,which was made apparent by the yeast deposited on the upper part of theside wall andV the bottom-is used. The manner in which th apparatusworks is as follows:

Vsel the prismatic trough 2l which narrows off at Vfermentation liquidis supplied through the pipe 2 and can be regulated by the valve 2l. Thefermentation liquid passes through the device 2l, which is providedpreferably at the top with small openings, into the suspension zone Il(Figure 4) within the prismatically disposed guiding surfaces 29. At thesame time air is introducedv into the air space 21 through the pipe 25and regulating valve .26; this air is finely divided by the airsubdivid'ing device A(filter 28) The ascending air at the' same timesucks up fermentation liquid ,from below and any excess yeast mud whichmay be present. At the top edge .of the guiding surfaces 29 the liquidenters the circulation zone 5I (cf. Figure 4). A part of the liquidgets` into the suspension space again at the"` lower end of the guidingsurface 29 whilst another part ows into the inclined surface system 3|,32 and I3.

Y The baille surface III which is shown is advisable but is notabsolutely necessary. 'Ihe yeast still,

present in the fermentation liquid deposits on the inclined surfaces 3i,32 and Il whilst the liquidfreed fr om the yeast can be withdrawnthrough the run-off pipe 34. The rate of flow between v the individualinclined surfaces may amongst other things alsov be regulated bycontrolling the withdrawal '(by means of valve 35) in which case aseparate regulable withdrawal device may be 'arranged between each twoinclined surfaces.

The yeast which settles on the inclined surfaces Il, l2 and and on theinclined wall of the trough 2l slides to the bottom vand is\.col

a way thatvreagitation of the vyeast is avoided.`\

'Ihe collecting yeast mud can be withdrawn by means of the pipe 31 andclosure member Il.

In Figure 4` the three zones of 'the fermentation apparatus, thesuspension zone SII, the settlingl w zone M and the circulation zone 5iare indicated 52 are distinguished by shading. The rcircula-I wideningpath, depositing yeast from the liquid.

schematically. The individual zones 5U, 5I and which consists in thisthat in view of the high yeast concentration `present in the suspensionspace only comparatively small quantities of air are used.

What we claim isz- 1. A method of fermenting solutions and producingyeast which comprisescausing a circulation along a path containing anupwardly and a downwardly directed portion within a bulk of fermentationliquid Acontaining yeast in suspension, continuouslysupplying freshnutrient solu. tion to vthe fermentation liquid at the beginning of theascending portion of said circulation path,

conducting the descending fermentation liquid from the circulation-pathinto an upwardly by gravity action in said upwardly widening path,guiding the depositing yeast under the action of gravity to theproximity of the beginning of` the ascending portion of the circulationpath where-- e by yeast is resuspended in the liquid traversing lectedby the funnel-shaped ydevices I8 in such the circulation path, andcontinuously withdrawing' used liquid from the bulk of fermentationliquid at the top of the upwardly widenln path.

2. A-method as claimed in claim 1 in which the circulation within thebulk of fermentation liquid is leffected by mechanical means moving theliquid in the ascending portion of the circulation path'.

3. Amethod as claimed in claim 1 in which finely divided gas isintroduced into fermentation liquid at the bottom of the ascendingportion of the circulation path, which gas assists the ascenl sion ofthe liquid in this portion of the path.

4. A method as claimed in claim 1 in which the rate of iicw of thefermentation liquid is changed at at least one point.

5. A method as claimed in claim l in which the rate of flow of thefermentation liquid is changed at at least one place of transition froma descending flow to an ascending ilow.

6. A method as claimed in claim 1 in which the yeast withdrawn issubjected to an after-ripening process.

7. A method as claimed in claim 1 in which fresh yeast is added asseeding material to the fermentation liquid in the circulation path.

8. A method as claimed in claim l in which lvlvielod sugar wort is usedas the fermentation liq- 9. A method as claimed in claim 1 in which inga fermentation solution containing yeast in suspension to flow in anupwardly and downwardly directed path, and then vcausing the solution toilow and contact inclined surfaces on which the yeast is deposited andslides by gravit to the place of collection.

13. In a method of fermenting solutions and producing yeast, the stepswhich comprise causing a fermentation solution containing yeast insuspension to cw in an upwardly and downwardly directed path. and thencausing the solution to flow at a rate ofspeed slower than it owed insaid directed path and contact inclined surfaces on which the yeast isdeposited and slides by gravity to the place of collection.

14. A method of fermenting solutions and producing 'yeastwhich'comp'rises causing a fermentation solution containing yeast'insuspension to flow in an upwardly and downwardly directedl is depositedand slides by gravity tothe place of collection. and continuouslywithdrawing the liq- Y uid from which the yeast has beenl deposited.

` HEINRICH BCHOLLER. RUDOLF EICKEMEYER.

